[ros-users] multi-master support for Fuerte

Thu Sep 8 16:06:18 UTC 2011

I've been using foreign_relay in a multi-robot scenario utilizing tcp over an intermittent wifi connection.  It would be curious to see what others want in a multi-master system though--Ken, have you compiled a list of use cases during the BuildingManager discussions?

I could start by implementing a system that supports most of what users want rather than something so low level that everyone has to re-implement what they need.  I'm not saying that foreign_relay isn't great, I'm just saying it's not a complete solution.

My personal wishlist for a multi-master system in ROS is:
- native master discovery (mDNS?) or "find me all the robots available on my network"

- topic/service discovery with the concept of "public" topics that a master is exporting with various policy levels (read-only and read-write topics to start) 

- proper handling of dropped network connections
   - e.g. topic notification or master callback handlers for connection changes--with maybe a default that just creates WARNING/ERROR logs on the subscribers side

Anyone have anything they'd like to see in a multi-master solution that I didn't include?

NOTE: The wifi_comm package out of the ISR-UC repo more or less provides master discovery, but it operates on mesh networks instead of the more traditional wifi network topologies that personal indoor robotics employ (at least from my experience).

Jeff

> -----Original Message-----
> From: ros-users-bounces at code.ros.org [mailto:ros-users-
> bounces at code.ros.org] On Behalf Of Ken Conley
> Sent: Thursday, September 08, 2011 10:08 AM
> To: User discussions
> Subject: Re: [ros-users] multi-master support for Fuerte
> 
> On Thu, Sep 8, 2011 at 4:30 AM, Jeff Rousseau <jrousseau at aptima.com>
> <JRousseau at aptima.com> wrote:
> > Hey Folks,
> >
> >
> >
> > I haven't seen the topic brought up lately, so I'm not sure if someone is
> > already working on this for Fuerte-What is the state of multi-master
> support
> > in ROS and are there any plans for further development?
> 
> The Fuerte planning is in progress, but there are currently no plans
> on my end re: multi-master work.  During the Electric development
> cycle, we played around a bit with multimaster_experimental and
> developed the app_manager, which is one (of many) approaches for doing
> multi-master work. We started off wanting to do multi-robot, but
> rosjava refocused our efforts on using an Android device to interface
> with a robot -- similar techniques, but different assumptions.
> 
> Our general conclusion there was that multi-master is very
> application-specific as you have to make assumptions about
> connectivity and configuration in order to pull it off.  The
> app_manager has a master-syncing approach that works under good
> connectivity; more work is necessary to make it work under bad
> connectivity and really test it in multi-robot scenarios (it was
> generally used for multi-master, single robot use case).
> 
> I do plan on seeing what can be done in the wifi realm re: ROS, i.e.
> things that will improve a single master, multi-machine setup.
> 
> > I've been using
> > foreign_relay for a number of months and it mostly works, but I'd like to
> > see first-class multi-master support in ROS and am willing to commit
> > development time towards it.
> 
> Glad to hear it, what do you have in mind?
> 
> > PS I noticed "Building Manager" meeting notes which had discussions about
> > implementing proper multi-master support seems to have stalled...
> 
> See above.
> 
> cheers,
> Ken
> 
> >
> >
> >
> > Jeff
> >
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